The present invention relates to a digital automatic gain amplifier, and more particularly to a device for adjusting the amplitude of a reference signal to a predetermined level so as to permit subsequent data signals to be interpreted correctly.
A variable gain amplifying apparatus wherein the output of an amplifier may be veried by means of digital signals is disclosed in U.S. Pat. No. 3,470,487 granted to P. J. Lukas et al, on Sept. 30, 1969. Another automatic range changing circuit for attenuating stepwise the voltage output of a-current-to-volts amplifier is disclosed in U.S. Pat. No. 3,539,936 granted to John D. McGhee. Both of these devices teach varying the resistance in the feedback loop by means of electronic circuitry such as transistor switches. Normally, prior to analyzing signals stored on tapes the analyzing equipment being used has to be calibrated so that a calibration reference signal which preceded the data signals produces a predetermined voltage. Heretofore, usually this required manual adjustment by means of potentiometers, which was time consuming.